Four stroke dirt bikes were once overweight and underpowered, but that’s changing fast. Specialist off-road motorcycle manufacturer Husqvarna has disclosed details of a new 250 four-stroke engine it is testing that weighs just 22 kilograms. Though the motor may be small, there has been no significant saving in weight as the new bike, which is likely to be available in limited quantities by the end of the year, comes in at 92 kilos dry – the same as the Yamaha YZ250R and Suzuki RMZ250.